A.Protein kinase C project: The generation of novel chemical libraries of DAG-lactones using our constantly improved solid-phase method of synthesis continues to yield important lead compounds in various areas of potential therapeutic importance. The results on our first C1 domain-selective DAG-lactone with exclusive selectivity for RasGRP were published recently, as well as our results on DAG-lactones capable of stimulating alpha-secretase activity. Another DAG-lactone discovered this year was found to function as a very effective radiosentizer in vivo causing prostate-specific antigen (PSA) levels to drop to near zero when administered in conjunction with radiation. Large-scale syntheses of some of DAG-lactones were completed for in vivo studies, which are now in progress to investigate the increase in interferon production in combination with IL-12. In parallel to these findings, we continue to investigate the action of these DAG-lactones at the molecular level dissecting the interaction of the two chemically different carbonyl groups (sn-1 and sn-2) with the protein or membrane components. Two full papers addressing these issues were published late in 2005 and in early 2006. The syntheses of a new family or DAG-lactones containing aryl groups have been recently expanded. B.The progression toward the clinic for Zebularine [2(1H)-pyrimidinone riboside] was brought to an end last year by an unforeseen toxicity in rhesus monkeys, which was lethal when plasma levels reached 25 micromolar. This is in total contrast to the complete lack of toxicity in rodents (rats and mice), even at high doses. Efforts to circumvent the drug's toxicity and to improve the activity of zebularine at lower doses have been channeled in two directions: (1) Synthesis of a lipophilic prodrug of zebularine capable of delivering the 5'-monophosphate (ZMP), and bypassing metabolic activation and degradation. This is a joint effort with a German company (Heidelberg Pharma) and the University of Southern California. To that effect a Collaboration Agreement was signed with these two institutions to prepare and test the first candidate, and (2) The development of pro-drugs of 2'-deoxyzebularine, which are intended to deliver 2-deoxyzebularine-5'-monophosphate (dZMP). A number of 2'-deoxyzebularine prodrugs appear to work but only in the presence of added thymidine. Most likely, the dZMP generated inhibits two key enzymes, deoxycytidine deaminase and thymidylate synthase, and both are essential in maintaining normal thymidine levels.C.The use of stable NAD analogue, beta-methylene-TAD, synthesized at the LMC in years past and used for the high-resolution crystal structure of a mono-ADP -ribosylating toxin (similar to diphteria toxin) was highlighted in a paper published in Nature last year.